1. Field of the Invention
The present invention pertains to an adjustable adapter for lower leg prostheses having a spheroidal adapter head mounted within an adapter housing.
Prostheses for the knee, lower leg or foot are normally fastened to the bearer's bone using a prosthesis collar. To make the prosthesis adjustable at the desired angle and to make it possible to adjust it transversely to the prosthesis collar adapters for that purpose have previously been proposed.
2. Description of the Related Art
SE-B-8602143-3 describes a lower leg prosthesis equipped with such an adapter which includes a prosthesis collar attachment member for attachment to the lower collar of the prosthesis. On the side facing the prosthesis collar the prosthesis collar attachment member is screwed to an adapter element including a little hemisphere around the screw shaft, which hemisphere is made rotatable against a corresponding spheroidal inner surface in an adapter housing which is attached to a lower leg prosthesis at its opposite end. At a distance from the hemisphere there is a concentrically attached disc against which the prosthesis collar attachment abuts. Further, there are external bosses on the adapter housing equipped with threaded penetrating holes at an angle to the central axis in which pinning screws can be screwed in from below so that their front ends press against the disc attached to the hemisphere thus pressing the adapter housing to different angular positions relative to the adapter housing. The prosthesis collar attachment element has a penetrating hole of significantly greater dimensions than the fastening screws in it whereby using a washer it is possible to attach the prosthesis collar attachment element in different sideways adjustable positions relative to the adapter housing. Using this design it is possible to achieve different angular positions without detaching the prosthesis, but because of the small radius of the sphere the angular variation is relatively limited. At the same time a sideways adjustment can be achieved but for this it is necessary that the whole prosthesis including the prosthesis collar be detached to reach the side adjustment screws, all of which makes fitting more difficult.